DESCRIPTION: The long term objective is to understand in molecular terms what governs the transcription and replication of the vesicular stomatitis virus (VSV) genome. This virus continues to be an excellent model system for a large and important class of agents (Mononegavirales), which include major human pathogens such as measles, mumps, parainfluenza, and respiratory syncytial viruses. The focus of this proposal is on ATP-mediated regulation of the virally-encoded P-L polymerase complex. In the transcription mode, this complex synthesizes five mRNAs from a ribonucleoprotein template containing the negative sense, single-stranded RNA genome (11, 161 nt). In the replication mode, the same two viral proteins synthesize full length genomes and antigenomes (plus sense intermediates). Evidence of a role for ATP in regulating these two types of syntheses was obtained during the previous grant period. The specific aims will test three hypotheses: 1) VSV RNA synthesis is regulated by an ATP-binding site in the L polymerase protein subunit of the P-L complex; 2) distinct P-L complexes are responsible for transcription versus replication; and 3) L polymerase protein subunit interacts with the template-associated viral nucleocapsid protein (N) to regulate transcription and replication functions. These studies will address fundamental aspects of virus multiplication and provide the groundwork for the development of new vaccines, viral vectors, and antiviral agents.